The direct antiglobulin test (DAT), also known as the direct Coombs test, is a technique that detects antibodies coating a patient's red blood cells in vivo. Using various reagents, the test determines if the red cells are coated with immunoglobulin, complement, or both. The test is performed using polyspecific antiglobulin (containing both IgG and C3d components), IgG, C3d, and a saline control.
A positive DAT result can be seen in immune-mediated hemolysis, autoimmune hemolytic anemia, transfusion reactions, or with certain drugs.
The indirect antiglobulin test (IAT), or indirect Coombs test, is used to detect unbound antibodies to RBCs that may be present in the patient's serum. This test is performed in the pretransfusion workup phase to determine the compatibility of RBC units for a patient.
